Thermoacoustic effects in supercritical fluids near the critical point: Resonance, piston effect, and acoustic emission and reflection

摘要

We present a general theory of thermoacoustic phenomena in supercriticalfluids near the critical point in a one-dimensional cell. We take into accountthe effects of the heat conduction in the boundary walls and the bulk viscositynear the critical point. We introduce a coefficient $Z(\omega)$ characterizingreflection of sound with frequency $\omega$ at the boundary. As applications,we examine the acoustic eigenmodes in the cell, the response to time-dependentperturbations, sound emission and reflection at the boundary. Resonance andrapid adiabatic changes are noteworthy. In these processes, the role of thethermal diffusion layers is enhanced near the critical point because of thestrong critical divergence of the thermal expansion.